Influence of Changes in Blood Pressure on Cerebral Perfusion and Oxygenation

S. J.E. Lucas, Y. C. Tzeng, S. D. Galvin, K. N. Thomas, S. Ogoh, P. N. Ainslie
2010 Hypertension  
Cerebral autoregulation (CA) is a critical process for the maintenance of cerebral blood flow and oxygenation. Assessment of CA is frequently used for experimental research and in the diagnosis, monitoring, or prognosis of cerebrovascular disease; however, despite the extensive use and reference to static CA, a valid quantification of "normal" CA has not been clearly identified. While controlling for the influence of arterial PCO 2 , we provide the first clear examination of static CA in
more » ... humans over a wide range of blood pressure. In 11 healthy humans, beat-to-beat blood pressure (radial arterial), middle cerebral artery blood velocity (MCAv; transcranial Doppler ultrasound), end-tidal PCO 2 , and cerebral oxygenation (near infrared spectroscopy) were recorded continuously during pharmacological-induced changes in mean blood pressure. In a randomized order, steady-state decreases and increases in mean blood pressure (8 to 14 levels; range: Ϸ40 to Ϸ125 mm Hg) were achieved using intravenous infusions of sodium nitroprusside or phenylephrine, respectively. MCAv mean was altered by 0.82Ϯ0.35% per millimeter of mercury change in mean blood pressure (R 2 ϭ0.82). Changes in cortical oxygenation index were inversely related to changes in mean blood pressure (slopeϭϪ0.18%/mm Hg; R 2 ϭ0.60) and MCAv mean (slopeϭϪ0.26%/cm ⅐ s Ϫ1 ; R 2 ϭ0.54). There was a progressive increase in MCAv pulsatility with hypotension. These findings indicate that cerebral blood flow closely follows pharmacological-induced changes in blood pressure in otherwise healthy humans. Thus, a finite slope of the plateau region does not necessarily imply a defective CA. Moreover, with progressive hypotension and hypertension there are differential changes in cerebral oxygenation and MCAv mean . (Hypertension. 2010;55:698-705.)
doi:10.1161/hypertensionaha.109.146290 pmid:20083726 fatcat:suh5ev3wqjhr5b3ccma6t5zlcq